The present invention relates to a transmission mechanism for pneumatic tool, and more particularly to a transmission mechanism that can be conveniently mounted into a housing of a pneumatic tool and enables the pneumatic tool to operate more smoothly.
A general pneumatic tool 100 usually includes a transmission mechanism 1xe2x80x2 shown in FIGS. 1 and 2 show transmission mechanism 1xe2x80x2 mainly includes a case main 1 in which a front cover bearing 19, a front cover 20, a main body 12, a sleeve seat 13, a sleeve 14, and a spring 15 are sequentially mounted from bottom to top, and a transmission shaft 18 having an end projected from a top of the casing to extend through an oil-retaining shaft sleeve 17 via a washer 16. When the entire transmission mechanism 1xe2x80x2 has been mounted in a housing of the pneumatic tool 100, impact forces from two sources, namely, the transmission shaft 18, the washer 16, and the oil-retaining shaft sleeve 17, as well as the sleeve seat 13, the sleeve 14, and the casing 11, are transmitted to the main body 12, the front cover bearing 19, and the front cover 20 via two ends of the spring 15. When the pneumatic tool 100 is operated, each movement of the transmission mechanism 1xe2x80x2 would cause an impact on the main body 12 to result in deformation or breaking thereof, and on the front cover bearing 19 and the front cover 20 to result in undesired loosening and deformation thereof.
When the transmission mechanism 1xe2x80x2 rotates at a speed as high as 7000 rpm, the transmission shaft 18, the washer 16, and the oil-retaining shaft sleeve 17 are subjected to an action force of about 7 kgs from the spring 15 and therefore tightly contact with one another to result in reduced clearances and increased friction among them, as well as undesired heating of these components. The transmission mechanism 1xe2x80x2 therefore has slowed rotational speed, increased noise, and reduced torque output.
It is noted the main body 12, the sleeve seat 13, the sleeve 14, the spring 15, the washer 16, the oil-retaining shaft sleeve 17, and the transmission shaft 18 of the above-described conventional transmission mechanism 1xe2x80x2 for pneumatic tool 100 for assembled without being holding in place in the casing 11xe2x80x2 by locating means. When the primarily assembled transmission mechanism 1xe2x80x2 is to be mounted in this to be of the pneumatic tool 100, specially designed tools must be used. Moreover, the components of the primarily assembled transmission mechanism 1xe2x80x2 tend to separate from one another during movement or transport before being mounted into the housing of the pneumatic tool 100, resulting in inconveniences and additional time and labor in subsequent assembling.
It is therefore a primary object of the present invention to provide an improved transmission mechanism for pneumatic tool that is able to overcome the problems of deformed or broken main body, over tightly contacted transmission shaft, washer, and oil-retaining shaft sleeve, and inconvenient assembling, so that the pneumatic tool could be more easily assembled and smoothly operated.
To achieve the above and other objects, the transmission mechanism for pneumatic tool according to the present invention mainly includes a casing that has an extended length to allow for the provision of a locating groove along an inner peripheral surface close to a top thereof for receiving a C-shaped retaining ring therein, and a washer that is provided at one side facing toward the top of the casing with a boss portion. After the transmission mechanism is assembled, the C-shaped retaining ring firmly bears against one side of the washer around the boss portion to hold the transmission shaft in place in the casing.
With the C-shaped retaining ring, (1) the whole transmission mechanism is highly stably assembled and can therefore be more conveniently mounted in the housing of the pneumatic tool without easily separated components during transport and mounting of the transmission mechanism; (2) undesired deformation or breaking of the main body caused by impact forces transmitted thereto from the transmission shaft via the spring can be eliminated; and (3) the washer is protected from overly tight contact with said oil-retaining shaft sleeve to avoid undesired friction, noise, heating, and reduced torque output of said transmission mechanism.